A MEMS Capacitive Microphone Modelling for Integrated Circuits

In this paper, a model for MEMS capacitive microphone is presented for integrated circuits. The microphone has a diaphragm thickness of 1 μm,0.5 × 0.5 mm2 dimension, and an air gap of 1.0 μm.Using the analytical and simulation results, the important features of MEMS capacitive microphonesuch as pull-in voltage and sensitivity are obtained as 3.8V and 6.916 mV/Pa, respectively, while there is no pressure on the diaphragm. The microphone has a capacitance of 2.3 pF. Using the relationbetween the capacitance and pressure signal, a 3 ports model for the MEMS microphone is proposed.To bias the microphone, a 2.3 V DC and a 1 GΩ resistor is used. The voltage and current signal of the microphone is proportional to the applied pressure of the acoustic wave. An RC filter is added to the circuit to eliminate the low band frequency (≤ 20 Hz) noises. The microphone shows good response to amplitude and frequency changes versus applied pressure signal

Keywords:

MEMS , Integrated Circuits , Modeling , Capacitive microphone , Pull-in voltage ,